Answer: b. declining birthrates.
Explanation:
The southern economies of the world such as in Africa and South America have not fared as well as the northern countries of Europe and North America as the former lags well behind the latter in many ways.
One way they do not lag behind however, is birth rates. The Southern countries have high birth rates and keep adding to the global population at a time when the Northern countries are slowing down their birth rates with some even experiencing negative population growth.
